Phosphorus pentachloride decomposes according to the chemica

Phosphorus pentachloride decomposes according to the chemical equation PCI5(g) PC13(g) + Cl2(g) =1.80 at 250°C A 0.200 mol sample of PCls(g) is injected into an empty 3.10 L reaction vessel held at 250 °C. Calculate the concentrations of PCls(g) and PCl3(g) at equilibrium. Number PCI = Number PC131 =

Solution

           PCl5(g)   <----->    PCl3(g)     +   Cl2(g)

initial     0.2/3.1               0               0

           = 0.0645 M

change        - x                  + x            +x

equil       0.0645 -x               x              x

Kc = [PCl3][Cl2]/[PCl5]

1.8 = x*x/(0.0645-x)

x = 0.0623

at equilibrium

[PCl3] = x = 0.0623 M

[Cl2] = x = 0.0623 M

[PCl5] = 0.0645-0.0623 = 0.0022 M